Toyo Engineering Corporation

Shuhei Nakamura

Keigo Sasaki

Haruyuki Morikawa

Kenji Yoshimoto

Eiji Sakata

Keishi Sato

Akiko Sugiura

Akiko Ushifusa

Precipitation of an ammonium salt is prevented while suppressing an increase in water content of the aqueous urea solution which is to be supplied to a urea granulation step, when recovering and using urea and NHin a gas which contains urea dust and NHand which arises from a urea granulation step.

Method for granulating urea

The present invention is a urea production method, including: a first concentration step of concentrating an aqueous urea solution; a granulation step of producing solid urea from the concentrated urea solution generated in the first concentration step; a urea recovery step of treating exhaust gas from the granulation step and recovering urea dust in the exhaust gas to generate a recovered aqueous urea solution, the granulation step being configured so as to treat a concentrated urea solution containing an additive; and a second concentration step of concentrating the recovered aqueous urea solution as an additional concentration step, wherein the concentrated recovered urea solution generated in the second concentration step is joined to the concentrated urea solution in the downstream of the first concentration step, and an additive is added downstream of the first concentration step.

Urea production method

The present invention relates to a method for producing a high-purity aqueous urea solution, utilizing a urea production process at least including a urea synthesis step of synthesizing urea from a raw material feed to produce a urea synthesis liquid, and a urea purification step of purifying the urea synthesis liquid to produce an aqueous urea solution with high urea concentration. The present invention includes a urea crystallization step of separating a part of the urea synthesis liquid and/or a part of the aqueous urea solution and crystallizing urea contained in the separated urea synthesis liquid and/or aqueous urea solution to produce solid crystal urea, and a mixing step of mixing the crystal urea with water to produce a high-purity aqueous urea solution. A high-purity aqueous urea solution to be produced is an aqueous urea solution with high purity suitable as a reducing agent for SCR.

Method for producing high-purity aqueous urea solution in urea production process

There are provided a method for analyzing an aqueous ammonium carbamate solution whereby the composition of an unreacted-gas absorber outlet liquid can be specified in real time, and a method for operating an unreacted gas absorber by use of the same. The method for analyzing the composition of an aqueous ammonium carbamate solution includes determining ammonia component concentration, carbon dioxide component concentration, and water concentration of the aqueous ammonium carbamate solution, which is the unreacted-gas absorber outlet liquid in a urea production process, by using a correlation among viscosity, temperature, and carbon dioxide component concentration of the aqueous solution and a correlation among density, temperature, ammonia component concentration, and carbon dioxide component concentration of the aqueous solution, wherein the ammonia component concentration is a concentration of a sum of free ammonia and equivalent ammonia of ammonium carbamate which are contained in the aqueous solution, and the carbon dioxide component concentration is a concentration of equivalent carbon dioxide of ammonium carbamate contained in the aqueous solution.

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Narashino, Japan

Shuhei Nakamura